This project is composed of two major areas of research: (1) studies of pyrimidine nucleotide synthesis in vivo and (2) cellular control of nucleoside diphosphate sugar synthesis and glycosaminoglycan formation. The relative contribution of de novo and salvage synthesis to tissue pyrimidine nucleotide pools is an important parameter in the rational design of antipyrimidine therapies. Both pathways were measured in the intact mouse using stable isotopes to quantitate de novo activity and radiolabled uridine to quantitate salvage. All murine tumors studied to date rely on de novo synthesis and most do not switch to the salvage pathway when the de novo pathway is blocked. One murine tumor (Nettesheim carcinoma) responded to PALA treatment by stimulating salvage; this tumor will be used to determine the therapeutic benefit of concurrent inhibition of both pathways. Normal mouse tissues studied utilize a balance of both pathways and do not enhance salvage in response to a block of de novo. Dietary nitrogen was found to enhance de novo synthesis in intestine and to protect mice from the toxic effects of PALA and 5-FU; there was no enhancement in B-16 melanoma. Thus dietary nitrogen could be used to enhance the differential toxicity of these agents Data from our Laboratory support a link between mitogen-stimulated synthesis of the glycosaminoglycan hyaluronate and the activation of pathways responsible for the synthesis of nucleoside diphosphate sugars which are precursors for hyaluronate and the oligosaccharide moieties of other GAGs. Data indicate that hyaluronate synthesis in fibroblasts can be stimulated by regulatory peptides released by carcinomas. Potential inhibitors of enzymes of the hyaluronate pathway are under study for their ability to block mitogen-induced GAG synthesis. Active agents will be evaluated for anti-invasive and anti-metastatic properties.